This invention relates to a new and unique inbred tetraploid watermelon line, designated 51WA009.
Watermelon is an important horticultural crop that accounts for 2% of the world area devoted to vegetable crops. There were 3,810,535 hectares (Ha) of watermelon grown in the world, and 51,110 Ha of watermelons grown in the United States in 2009. Asia is by far the most important watermelon production site with 78% of the world area and 83.4% of the world production of 100,687,056 metric tons. The estimated annual world watermelon value exceeded $7.6 billion when using the United States average price for 1995-1997. Watermelon is grown in at least forty-four states in the United States, with Florida, Georgia, California, and Texas, having long warm growing seasons, being the major producing states. In the United States, watermelon production has increased from 1.2 M tons in 1980 to 3.8 M tons in 2009, with an annual farm value of $470 million (U. S. Department of Agriculture, Agricultural Statistics, 2009).
In recent years, there has been an increase in consumer demand for seedless watermelons, and production of seedless watermelon has increased significantly. Triploid seedless watermelons have been commercially grown in the United States since the late 1980's. Currently, over 80% of the watermelons produced in the United States are triploid seedless watermelons. Seedless watermelon receives well above the average price for seeded watermelons in the market. Triploid seedless watermelon also produces higher yields than the diploid seeded watermelons.
Triploid seedless watermelon is a true F1 hybrid between a tetraploid watermelon, as the female parent, and a diploid watermelon, as the male parent (Kihara, H. 1951, Triploid Watermelons, Proceedings of American Society for Horticultural Science, 58:217-230). Diploid watermelons have 22 chromosomes (2N=2X=22) in their somatic cells, and tetraploid watermelons have 44 chromosomes (2N=4X=44) in their somatic cells. Cells with three sets of homologous chromosomes are said to be triploid and are designated as 3X. When female flowers of tetraploid plants are cross pollinated by the male flowers of diploid plants, the fruits produced by the tetraploid plants contain triploid seeds that produce triploid plants. The triploid seedless watermelons have 33 chromosomes (2N=3X=33) in their somatic cells. When the triploid plants are grown with diploid plants in the same field, the triploid plants produce fruits that are seedless. The seedless condition in triploid watermelon is the result of the presence of three homologous sets of chromosome per somatic cell rather than the usual two. The inability of the triploid zygote to produce normal viable gametes (pollen and egg cells) causes the absence of seeds in triploid fruits. Typically, seedless watermelons contain small edible white ovules, similar to those in immature cucumbers.
Watermelon, in general, and seedless watermelon in particular, is an important and valuable vegetable crop. Thus, there is an ongoing need for improved inbred tetraploid watermelon lines.